1. Field of the Invention
The present invention relates to a method for producing a piezoelectric actuator which includes a piezoelectric layer, and a method for producing a liquid transport apparatus which includes such a piezoelectric actuator.
2. Description of the Related Art
In relation to an ink-jet head described in Japanese Patent Application Laid-open No. 2006-54442, a piezoelectric actuator, which applies the pressure to the ink contained in a pressure chamber, is produced in accordance with the following procedure. At first, a vibration plate, which is composed of, for example, a stainless steel material, is joined to an upper surface of a channel unit to cover the pressure chamber therewith. A lower electrode, which serves as a diffusion-preventive layer (diffusion barrier layer), is formed on an upper surface of the vibration plate. A piezoelectric layer is formed thereon by means of the aerosol deposition method (AD method). Further, the annealing, in which the piezoelectric layer is heated at a high temperature, is performed in order that the piezoelectric layer, which is formed by the AD method, has the piezoelectric characteristic. During this procedure, constitutive atoms of the vibration plate, which are heated together with the piezoelectric layer, are diffused. However, the diffusion of the atoms is stopped at the lower electrode which serves as the diffusion-preventive layer. The constitutive atoms of the vibration plate are prevented from being diffused into the piezoelectric layer. Accordingly, the deterioration of the piezoelectric characteristic of the piezoelectric layer, which would be otherwise caused by the diffusion of the constitutive atoms of the vibration plate into the piezoelectric layer, is suppressed.
In the case of the piezoelectric actuator described in Japanese Patent Application Laid-open No. 2006-54442, the pressure is applied to the ink contained in the pressure chamber by deforming the portion (active portion) of the piezoelectric layer opposed to the pressure chamber. Therefore, the piezoelectric characteristic of the portion of the piezoelectric layer opposed to the pressure chamber affects the driving of the piezoelectric actuator. However, in the case of the ink-jet head described in Japanese Patent Application Laid-open No. 2006-54442, the vibration plate, which is composed of, for example, the stainless steel material, is arranged at the portion of the piezoelectric layer opposed to the pressure chamber. Therefore, even when the lower electrode, which serves as the diffusion-preventive layer, is arranged between the piezoelectric layer and the vibration plate, the lower electrode cannot sufficiently stop the diffusion of the constitutive atoms of the vibration plate. Therefore, the constitutive atoms of the vibration plate pass through the lower electrode, the constitutive atoms are diffused into the portion of the piezoelectric layer opposed to the pressure chamber, and the piezoelectric characteristic of the concerning portion of the piezoelectric layer is deteriorated. As a result, it is feared that the amounts of deformation of the piezoelectric layer and the vibration plate may be lowered when the piezoelectric actuator is driven.